Multiple wells are often drilled on a single well pad. The same drilling rig may be used to drill and/or service multiple wells on a well pad. For example, the same drilling rig may drill each of three wells spaced apart approximately 25 feet on a well pad. To drill the wells, the drilling rig drills a surface section, which may be about 1000 feet deep. After drilling the surface portion, the drilling mud is changed to allow the drilling rig to drill the intermediate section, which may have a depth of 1000-6000 feet. After drilling the intermediate section, the drilling mud is once again changed to allow the drilling rig to drill the completion portion. The completion portion may be 6000 or more feet deep and may include 1000 or more feet of horizontal drilling.
In such a multi-well program it is common to assemble the drilling rig on the well pad, drill the surface section of the first well, then use hydraulically actuated shoes to walk 25 feet over to the next well and drill that surface section, without changing the drilling mud. In this manner, three surface portions may be drilled sequentially without requiring a change of the drilling mud. Once the three surface sections are drilled, the drilling mud can be changed, and the three intermediate sections can be drilled sequentially. The same drilling procedure may be used for the completion section of all three wells.
Conventional walking drilling rigs rely on unfolding electrical and flow lines in connection with walking of the drilling rig because certain equipment associated with the electrical and flow lines does not move with the drilling rig. In addition, the rig up or assembly of a drilling rig is inefficient because important components are transported on separate vehicles and are assembled manually at the well pad. For example, oftentimes the components that make up a drilling rig's substructure are shipped on three separate trucks and must be assembled on the well pad. A substructure typically includes a base, legs that are supported by the base, and a drill floor that is supported by the legs. Workers are often elevated to near drilling height to perform the manual assembly. Once assembled, substantial disassembly may be required to facilitate walking of the drilling rig. Once the drilling rig has walked to the next well, the disassembled components must be reassembled for the drilling rig to be fully operational to drill and/or service the next well.